Evidence Grows that Wild Birds May Transmit IB

UK - Researchers at the University of Liverpool have found genetically diverse coronaviruses in wild bird populations in northern England, adding to the evidence that wild birds may transmit infectious bronchitis (IB) virus to poultry.

In their paper published in Emerging Infectious Diseases, Hughes and colleagues at the University of Liverpool say that they detected diverse coronaviruses by PCR in wildfowl and wading birds in England, and that sequence analysis showed some viruses to be related to infectious bronchitis virus (IBV).

In their introduction, Hughes and colleagues explain that IBV, a group 3 coronavirus, causes a costly viral disease of chickens that is found worldwide. It can cause respiratory disease in chickens of all ages and a loss of production and egg quality in mature hens. Some strains are nephropathogenic, resulting in renal-induced mortality rates of up to 25 per cent for susceptible flocks. Currently, the poultry industry controls disease through the use of vaccines.

The authors state that IBV continuously generates antigenic variants and that current vaccines offer no protection against some of them. Wild birds may play a role as both reservoirs and long-distance vectors of IBV.

Recent research has shown that group 3 coronaviruses genetically similar to infectious bronchitis virus were detected in healthy birds of the chicken family and other, which suggests that wild birds are able to carry IBV-like viruses asymptomatically.

The group from Liverpool collected samples from 441 individual wild birds of 42 species, including both migratory and resident species, in a series of cross-sectional surveys of wild bird populations throughout northern England between July 2004 and January 2007.

Coronavirus RNA was detected only in wildfowl (Anseriforms) and waders (Charadriiformes). Sequence analysis of the viral DNA showed that some of the viruses were related to IBV.

"The detection of coronaviruses that appear to be related to IBV in wild migratory birds raises interesting questions as to their role in the transmission, dissemination, and evolution of IBV strains," say the authors of the paper.